Bivalents are formed in

Options

A. diplotene
B. pachytene
C. zygotene
D. interkinesis

Answer

To determine where bivalents are formed, we need to analyze the stages of meiosis and identify the correct stage associated with the formation of bivalents (homologous chromosomes).

### Step-by-Step Solution:

1. **Understanding Bivalents**:
- Bivalents are pairs of homologous chromosomes that come together during meiosis. Each bivalent consists of two homologous chromosomes, each made up of two sister chromatids.

2. **Identifying the Stages of Meiosis**:
- Meiosis consists of several stages: Prophase I, Metaphase I, Anaphase I, Telophase I, and then Meiosis II. Prophase I is further divided into five substages: Leptotene, Zygotene, Pachytene, Diplotene, and Diakinesis.

3. **Analyzing Each Option**:
- **Option A: Diplotene**: In this stage, homologous chromosomes begin to separate but are still held together at chiasmata. Bivalents are not formed here; they are already present.
- **Option B: Pachytene**: This is the stage where bivalents are fully formed. Homologous chromosomes are closely paired, and crossing over occurs.
- **Option C: Zygotene**: During this stage, homologous chromosomes begin to pair up, but the bivalents are not yet fully formed.
- **Option D: Interkinesis**: This is a resting phase between meiosis I and II, and bivalents are not formed during this stage.

4. **Conclusion**:
- The correct answer is **Option B: Pachytene**, where bivalents (homologous chromosomes) are formed.

### Final Answer:
Bivalents are formed in **Pachytene**.

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